Caffeine Crash: What Causes It and How to Avoid It
Most of what people call a caffeine crash is tiredness the caffeine was covering, plus withdrawal, short sleep or sugar. Here's what the studies show and what helps.
Short answer
A caffeine crash is the drop in energy some people feel as caffeine wears off. It isn't a medical diagnosis. The studies point to four things behind it: tiredness the caffeine was masking, withdrawal in regular users, short sleep and sugar. A steady daily dose, enough sleep and less sugar help the most.
The coffee stops working around 3 p.m. and you feel worse than you did before it. I wanted to know whether that's a real effect or just a feeling, so I read the studies on caffeine withdrawal, sleep loss, sugar and the afternoon dip. The crash turns out to be several different things that people lump together, and each one has its own fix.
What is a caffeine crash?
There's no clinical definition. The closest defined condition is caffeine withdrawal, which became an official diagnosis in the DSM-5, the psychiatric diagnostic manual.
The best description of the everyday version I found comes from a 2007 survey of college students. The researchers called it a "jolt and crash episode": a feeling of more alertness and energy, followed by a sudden drop. Of 253 students who drank energy drinks, 29% had one every week. It was the only side effect in the survey that rose with how much people drank.
That's self-reported data from one campus. It shows the crash is common but says nothing about the cause. For that you have to look at what caffeine does in the brain.
Why does caffeine make you crash?
Caffeine blocks adenosine receptors. Adenosine is one of the signals behind sleep pressure. In a 1997 study in cats, adenosine in one area of the brain rose the longer the animals stayed awake and fell slowly during sleep.
Caffeine stops adenosine from acting on its receptors, but nothing in these studies suggests it gets rid of the adenosine. So when the caffeine wears off, the tiredness that built up all morning is still there. That's the usual explanation for the crash, though I didn't find a human study that tested it directly.
For regular coffee drinkers there's a second effect, and the evidence for it is better. In a 2010 study of 379 people, everyone went 16 hours without caffeine. Afterwards, medium and heavy users who got a placebo felt less alert and had more headaches. People who rarely used caffeine didn't get more alert from it at all.
The authors concluded that for regular users, caffeine mostly brings alertness back to baseline after a night without it. A 2005 review came to the same view: most of the "boost" seen in studies comes from reversing the withdrawal effects of a short break from caffeine. Once you drink coffee daily, your normal without it sits lower, so a skipped or late coffee hits harder.
What does a caffeine crash feel like?
I found no symptom list for the same-day crash, but caffeine withdrawal is well studied. A 2004 review of 66 studies confirmed these symptoms:
- headache
- fatigue, low energy and drowsiness
- lower alertness and difficulty concentrating
- feeling foggy or not clearheaded
- irritability, low mood and feeling less content
Flu-like symptoms, nausea and muscle pain or stiffness were judged likely too. In the experimental studies, about half of the people got a headache, and 13% had symptoms bad enough to cause real distress or get in the way of daily life.
When does a caffeine crash happen, and how long does it last?
That depends on the cause, and each one runs on a different clock:
| Cause | Timing in the studies |
|---|---|
| Sugary drink or carbs | More fatigue within the first hour. Slower reactions about 80 minutes after one sugary energy drink. |
| Afternoon dip | Mid-afternoon, with or without lunch |
| Caffeine withdrawal | Starts 12 to 24 hours after the last dose, peaks at 20 to 51 hours, lasts 2 to 9 days |
| Short sleep | Caffeine stopped helping by day 4 of 5-hour nights |
Caffeine itself has a half-life of about 3 to 6 hours in healthy adults (I covered that in how long caffeine stays in your system). So half of an 8 a.m. coffee is gone sometime between 11 a.m. and 2 p.m., around the time the afternoon dip sets in. That's my own arithmetic, not a measured result, but it would explain why so many people feel the drop at about the same time of day.
Is a caffeine crash really just sleep debt?
Often, at least in part. A 2017 study at the Walter Reed Army Institute of Research put 48 healthy people on five nights of 5 hours in bed. One group chewed gum with 200 mg of caffeine at 8 a.m. and noon, the other a placebo gum.
Caffeine kept them more alert than placebo for the first three days. By day four the difference was gone. The caffeine group also took longer to get back to normal alertness during the recovery nights.
A 2008 review by two sleep researchers adds that when people sleep their usual amount, caffeine mostly restores performance that sleepiness had dragged down. It also linked regular caffeine use to worse sleep and more daytime sleepiness. That can turn into a loop. Late caffeine cuts your sleep, you feel worse the next afternoon, and you reach for more.
Does sugar make a caffeine crash worse?
The evidence says yes, or at least that sugar doesn't help. A 2019 meta-analysis pooled 31 studies with 1,259 people and found no mood benefit from carbohydrates at any point. Within the first hour, people who had them were more tired and less alert than those on placebo.
One small trial tested a sugary energy drink directly. Ten people slept only 5 hours, ate a light lunch, and then drank either 250 ml of an energy drink with 42 g of sugar and 30 mg of caffeine, or a sugar-free, caffeine-free version. The energy drink didn't reduce sleepiness, and about 80 minutes later reaction times were slower, with more lapses. Ten people is a tiny sample, but it fits the larger analysis.
How do you avoid a caffeine crash?
These are the changes the studies support, roughly in order of how much I'd expect them to help:
- Get enough sleep. On 5-hour nights, caffeine stopped working by day four in the Walter Reed study.
- Keep your daily amount steady. Withdrawal showed up after as little as 3 days of 300 mg a day in a 1999 study, and even people on 100 mg a day got it when they stopped. Taking the 300 mg as one morning dose or as three 100 mg doses made no difference to withdrawal.
- Cut down in steps if you want to use less. In that same study, people used to 300 mg a day only developed withdrawal once they dropped to 100 mg or less.
- Skip sugary energy drinks when you're already tired.
- Stop caffeine earlier in the day. In a 2013 trial, 400 mg taken 6 hours before bed still cut sleep by more than an hour.
For the afternoon slump specifically, a short nap combined with caffeine worked better than caffeine alone in a driving study. Twelve sleepy people had a 30-minute break before a 2-hour simulated drive in the afternoon. With placebo, sleepiness and driving errors peaked mid-afternoon. Caffeine alone cut incidents to 34% of the placebo level. Caffeine plus a nap of under 15 minutes cut them to 9%. Even people who only dozed without fully falling asleep benefited.
How do you recover from a caffeine crash?
If it's the ordinary afternoon drop, the driving study above is the best evidence I found: a coffee and a nap of under 15 minutes. If you can't nap, go easy on a high-carbohydrate lunch, which a review of the post-lunch dip says makes the slump worse.
If it's withdrawal, because you skipped your usual coffee, the symptoms fade on their own within 2 to 9 days. Caffeine reverses them, which is probably part of why the first coffee of the day feels so good. If you're cutting back on purpose, step down. In the 1999 dosing study, people used to 300 mg a day had no withdrawal when cut to 200 mg, though nobody compared stepping down with quitting outright. A 2016 trial used a 5-week step-down plan, and people kept their caffeine use lower for up to a year. That trial measured how much caffeine people used, not how bad their symptoms were.
If it's sleep debt, more caffeine only buys you a few days, going by the Walter Reed study, and the way out is sleep.
Does time-release caffeine prevent a crash?
Our Deadline Focus Pill has about 137 mg of caffeine per 3-capsule serving, most of it in a time-release form, plus 200 mg of L-theanine (I went through the caffeine and L-theanine studies separately). There's no sugar in it.
What I can say about time-release caffeine is limited. In one small study run by the maker of a different extended-release caffeine, blood levels peaked after about 4 hours, against under 1 hour for regular caffeine, and people rated themselves less tired and less jittery 8 to 12 hours later. The study was open-label with 15 people. I found no study that measured a crash with any time-release caffeine, including ours. A slower release also does nothing for sleep debt or withdrawal, so the advice above applies whatever caffeine you use.
Frequently asked questions
What does a caffeine crash feel like?
Usually a sudden drop in energy after the lift wears off. If it's withdrawal, the confirmed symptoms are headache, fatigue, drowsiness, trouble concentrating, feeling foggy, irritability and low mood.
How long does a caffeine crash last?
No study I found timed the afternoon slump itself. Caffeine withdrawal is better measured: it starts 12 to 24 hours after your last dose, peaks at 20 to 51 hours and lasts 2 to 9 days.
Is a caffeine crash real?
People report it often. In one survey, 29% of college energy drink users had a jolt-and-crash episode every week. It isn't a medical diagnosis, but caffeine withdrawal is, and it explains part of it.
How long after caffeine do you crash?
No study measured this directly. Caffeine's half-life is about 3 to 6 hours, so a morning coffee is half gone by late morning or early afternoon, which is also when the afternoon dip starts. Sugary drinks can make you more tired within an hour.
How do you stop a caffeine crash fast?
In one driving study, caffeine plus a nap of under 15 minutes cut driving incidents to 9% of the placebo level. Avoiding sugary drinks keeps it from getting worse. Neither fixes short sleep.
Can a caffeine crash cause anxiety?
Anxiety wasn't one of the confirmed caffeine withdrawal symptoms in the 2004 review, though irritability and low mood were. Caffeine itself can cause anxiety, mostly in people who rarely use it, and regular users build tolerance to that effect.
Limits of this evidence
No study I found measured the same-day caffeine crash in people directly. The adenosine build-up data comes from cats. Several trials here are small (10 to 15 people), and the energy drink survey is self-reported from one university. The withdrawal research is the strongest part, with dozens of controlled studies behind it. Nothing here is medical advice for your situation, and if you're pregnant, take medication or have a heart condition, ask your doctor about caffeine.
Sources
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Written by Nick. These statements have not been evaluated by the Food and Drug Administration. Deadline products are not intended to diagnose, treat, cure, or prevent any disease.